The present invention relates to hydraulic passages for an oil pump for a speed reducer used in electric vehicles.
There is an electric vehicle including an oil pump which is synchronously driven in the direction of rotation of a motor. In this electric vehicle which further includes a speed reducer coaxially disposed with respect to the motor, the oil pump is driven by rotation of the motor to produce a negative pressure under which liquid is sucked from a liquid reservoir arranged in a speed-reducer casing, and is discharged to a discharged-oil demand part.
With the speed reducer without a reverse gear, for example, switching of forward and reverse runs of the vehicle is carried out by switching of normal and reverse rotations of the motor. Thus, rotation of the oil pump is opposed upon forward and reverse runs of the vehicle, failing to supply an appropriate amount of discharged oil.
One of the solutions is, as seen in the Manual of New Model Car NISSAN TERRANO R50-0, p. C-30, published by Nissan Motor, Co., Ltd. in September, 1995, to provide another oil pump for reverse. However, this solution needs another control of the oil pumps or complicated arrangement of hydraulic passages for connecting the oil pumps.
It is, therefore, an object of the present invention to provide hydraulic passages for an oil pump for a speed reducer used in electric vehicles, which allow the oil pump, which is synchronously driven in the direction of rotation of a motor, to ensure a predetermined quantity of flow regardless of the direction of rotation of the motor.